Advancements in adaptive antenna matching techniques have provided gains in terms of, e.g., total radiated power. Matching techniques may be used to compensate for a number of conditions, such as environmental effects, user effects, etc.
Current techniques are based on sensing reflected power on the antenna port. For example, in connection with a mobile device, a directional coupler may be used on a transmit or uplink side to drive a tunable matching circuit so as to minimize reflected power. These techniques: (1) are iterative, (2) lack knowledge of the direction the tunable circuit should be tuned toward during the first iteration, resulting in the use of trial-and-error to determine the appropriate direction, and (3) tune the circuit to cover a transmit or uplink band and assume that coverage is broad enough to support antenna matching in the receive or downlink band.
Current techniques provide for a computation of the input impedance of the antenna using a perturbation approach. A first technique is applied in connection with the uplink or transmitter. A second technique is applied in connection with the downlink or receiver. Three power measurements are needed for each of the first and second techniques to compute the antenna impedance value and then match the circuit to the computed value. A measurement period must be long enough to accommodate the time needed to obtain the measurements.